(1) Field of the Invention
The present invention relates to a lubricating oil composition comprising a synthetic hydrocarbon lubricating oil as the base oil. More particularly, the present invention relates to a lubricating oil composition excellent in the compatibility with a load-withstanding additive.
(2) Description of the Prior Art
A refined petroleum type lubricating oil and a synthetic hydrocarbon type lubricating oil are known as typical examples of the lubricating oil.
The former refined petroleum type lubricating oil is easily oxidized and deteriorated because it contains structurally unstable double bonds. Furthermore, since the molecular weight is generally low (less than 500), the evaporation loss is large and the abrasion resistance is insufficient.
In contrast, the latter synthetic hydrocarbon type lubricating oil is structurally more stable than the former type lubricating oil, and the molecular weight can be adjusted within a broad range. Especially, if a specific monomer is selected and polymerized, it is possible to give such characteristics as a low pour point and a high viscosity index to the lubricating oil.
However, this synthetic hydrocarbon type lubricating oil is poor in the compatibility with a load-withstanding additive generally incorporated into a lubricating oil, and therefore, the use of this lubricating oil is restricted.